1. Field of the Invention:
The present invention relates to sea clutter suppression radar.
2. Description of the Prior Art:
Conventionally, a prior art technique is known as a prior one is disclosed in "STUDIES CONCERNING THE IMPROVEMENT OF THE SIGNAL-TO-CLUTTER RATIO OF RADAR-DETECTED SHIP TARGETS" by Specker, 1985, XI.sup.th CONFERENCE OF INTERNATIONAL ASSOCIATION OF LIGHTHOUSE AUTHORITIES.
It is often experienced, when a radar senses any target on the sea, that the radar may receive not only a true signal reflected from the target but also a false signal reflected from waves on the sea and thus be hindered from sensing the target. There are various known techniques to suppress such a reflected signal from waves on the sea, among which a technique to correlate those signals is widely known to be effective. The correlation method is to correlate a target signal with a reflected signal from the sea surface by making use of addition and multiplication or a combination thereof, etc., when those signals are varied temporarily or owing to a change in the characterisitcs of the associated radar waves. However, signals reflected from the sea surface are changed slowly in time compared with the period of a pulse from a radar. The method to take the correlation between signals shifted in time to each other or between signals changed in their planes of polarization to each other or the method in combination thereof is accordingly incapable of affording sufficient effects. To solve this, a technique was developed to take the correlation by varying the frequency of the radar waves. That is, the technique is adapted to take multiple correlation among four signals: two orthogonal polarized waves and two frequencies as disclosed in the aforementioned reference.
However, such a technique to use a plurality of frequencies suffers from a problem that it must occupy many frequencies having public character so that the associated radar equipment is complicated and costly.